Kenya's Lake Research Articles

Having a Blast in Kenya

![Figure][1] CREDIT: PETER HOEY/[PETERHOEY.COM][2] Our task? To position and detonate two 1000-kilo explosive charges on the bottom of Kenya's Lake Turkana. The year was 1990, and these blasts would allow seismometers placed up and down remote parts of the East African Rift to record sound waves from explosions and measure the structure of crust being pulled apart. To collect accurate data, we had to detonate the explosions exactly on time. As an inexperienced graduate student, my job was to pilot the Zodiac raft laden with plastic explosives. Setting the charges on the glassy lake in the morning was easy; we just had to pitch the explosive sausages overboard into a big pile on the lake bottom. We cleverly marked the shot locations with buoys made from empty water jugs anchored with rocks. Returning in the afternoon, we found that the wind had stirred up the lake surface into considerable swells. Finding the small white buoys in a sea of whitecaps was challenging. We found the first of the two, attached the electrical line, reeled off 500 feet of cable, and detonated without incident. But now we had only 10 minutes to find the second, and the wind was fierce. After 9 minutes, we located the small jug. We had time to back off only about 100 feet before hitting the button. The result? Nothing. What we didn't know was that the wind had blown the buoy about 100 feet away from the charge, dragging its inadequate anchor with it. That shift placed us directly above the explosives. So, although we didn't see the plume of water come off the shot, it wasn't long before we felt it. The blast launched the Zodiac and crew into the air. I dangled from the outboard motor and landed back in the lake with the raft, but my two companions were flung into the water. Luckily, the blast had scared the crocodiles away. Under a rain of dead tilapia and muddy water, we hauled back into the boat and started it up. Our only wounds were bruised bottoms from the force of the blast under us. We limped back to shore, where a Kenyan Ministry official had come to keep tabs on us and our effects on the fish. We approached him sheepishly, but he only commented that the second blast had seemed much smaller than the first. [1]: pending:yes [2]: http://PETERHOEY.COM

Analysis of Heavy Metals in Water and Surface Sediment in Five Rift Valley Lakes in Kenya for Assessment of Recent Increase in Anthropogenic Activities

The concentrations of heavy metals Ag, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sn and Zn were analysed in water and surface sediments of five Rift Valley lakes Nakuru, Elementaita, Naivasha, Bogoria and Baringo in Kenya. The dissolved mean concentration levels (mug/L) in water ranged within 13.0-185.0 (Ag), 2.0-43.0 (Cd), 5.0-316.0 (Co), 25.0-188.0 (Cr), 4.7-100.0 (Cu), 50.0-282.0 (Mn), 19.0-288.0 (Ni), 25.0-563.0 (Pb), 300.0-1050.0 (Sn) and 29.0-235.0 (Zn). The mean sediment concentrations (in mug/g (dry weight)) ranged within 0.1-0.35 (Ag), 0.05-1.18 (Cd), 0.17-1.38 (Co), 1.94-4.91 (Cr), 1.46-20.95 (Cu), 667.7-3946.8 (Mn), 11.69-39.72 (Ni), 10.92-38.98 (Pb), 17.21-56.52 (Sn) and 96.2-229.6 (Zn). The data indicate that some of the sites analysed, especially in Lake Nakuru, had relatively higher concentration levels of heavy metals Cd, Co, Cu, Pb, Ni, and Zn in the water which points to anthropogenic addition. However, potential influence of geochemical processes on the concentration levels in sediment is also shown in Co, Ni, and Cu which were more concentrated in the remote Lake Baringo sediment as well as in Pb and Mn which were more concentrated in the remote Lake Bogoria sediment. Data on some important limnological parameters including pH, salinity, electrical conductivity and temperature are also presented.

Establishing Viable Water and Wastewater Utilities in Kenya's Lake Victoria Watershed

Establishing Viable Water and Wastewater Utilities in Kenya's Lake Victoria WatershedThis paper describes the results of a water and wastewater feasibility study conducted for three towns in the Lake Victoria watershed of Kenya. Each town studied has a population of approximately 100,000 to 200,000 and all three are growing at rates sufficient to double their populations within 20 years. Deficiencies in water and wastewater infrastructure, operation, maintenance, and management...Author(s)D.S. FavazzaJ.J. ColantonioM.J. DevineC. LundstromSourceProceedings of the Water Environment FederationSubjectSession 114: International Approaches to SustainabilityDocument typeConference PaperPublisherWater Environment FederationPrint publication date Oct, 2007ISSN1938-6478SICI1938-6478(20071001)2007:8L.8831;1-DOI10.2175/193864707787781106Volume / Issue2007 / 8Content sourceWEFTECFirst / last page(s)8831 - 8858Copyright2007Word count269Subject keywordsKENYAAFRICAWATER AND WASTEWATER INFRASTRUCTUREUTILITY FINANCINGSUSTAINABILITY

Ian Parker. Jua Kali's Voyage on the Jade Sea. Moray, Scotland: Librario Publishing Ltd., 2004. xi + 228 pp. Maps. Photographs. Notes. Index. Appendix. £21.00. Cloth. - Kira Salak. The Cruelest Journey: 600 Miles to Timbuktu. Washington, D.C.: National Geographic, 2005. x + 230 pp. Map. $26.00. Cloth.

Ian Parker. Jua Kali's Voyage on the Jade Sea. Moray, Scotland: Librario Publishing Ltd., 2004. xi + 228 pp. Maps. Photographs. Notes. Index. Appendix. £21.00. Cloth. - Kira Salak. The Cruelest Journey: 600 Miles to Timbuktu. Washington, D.C.: National Geographic, 2005. x + 230 pp. Map. $26.00. Cloth. - Volume 50 Issue 1

A water index for rapid mapping of shoreline changes of five East African Rift Valley lakes: an empirical analysis using Landsat TM and ETM+ data

Because of the complicated shorelines, inaccessibility and vast spread of some lakes, information on changing shorelines is difficult to acquire. A new water index (WI) has been applied to quantify changes in five saline and non‐saline Rift Valley lakes in Kenya using Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) data. The WI is based on a logical combination of the Tasseled Cap Wetness (TCW) index and the Normalized Difference Water Index (NDWI). Using regression analysis with estimated shoreline coordinates, the WI detected the shorelines with an accuracy of 98.4%, which was 22.3% higher than the TCW, and 43.2% more accurate than the NDWI. Change detection was derived using image differencing followed by density slicing and unsupervised classification. The saline lakes (Bogoria, Nakuru and Elementaita) changed more with respect to the ratio of the change in the original surface areas than the non‐saline lakes (Baringo and Naivasha).

Fossil Chironomidae (Insecta: Diptera) as quantitative indicators of past salinity in African lakes

We surveyed sub-fossil chironomid assemblages in surface sediments of 73 low- to mid-elevation lakes in tropical East Africa (Uganda, Kenya, Tanzania, Ethiopia) to develop inference models for quantitative paleosalinity reconstruction. Using a calibration data set of 67 lakes with surface-water conductivity between 34 and 68,800 μS/cm, trial models based on partial least squares (PLS), weighted-averaging (WA), weighted-averaging partial least squares (WA-PLS), maximum likelihood (ML), and the weighted modern analogue technique (WMAT) produced jack-knifed coefficients of determination ( r 2) between 0.83 and 0.87, and root-mean-squared errors of prediction (RMSEP) between 0.27 and 0.31 log 10 conductivity units, values indicating that fossil assemblages of African Chironomidae can be valuable indicators of past salinity change. The new inference models improve on previous models, which were calibrated with presence–absence data from live collections, by the much greater information content of the calibration data set, and greater probability of finding good modern analogues for fossil assemblages. However, inferences still suffered to a greater (WA, WMAT) or lesser (WA-PLS, PLS and ML) extent from weak correlation between chironomid species distribution and salinity in a broad range of fresh waters, and apparent threshold response of African chironomid communities to salinity change near 3000 μS/cm. To improve model sensitivity in freshwater lakes we expanded the calibration data set with 11 dilute (6–61 μS/cm) high-elevation lakes on Mt. Kenya (Kenya) and the Ruwenzori Mts. (Uganda). This did not appreciably improve models’ error statistics, in part because it introduced a secondary environmental gradient to the faunal data, probably temperature. To evaluate whether a chironomid-based salinity inference model calibrated in East African lakes could be meaningfully used for environmental reconstruction elsewhere on the continent, we expanded the calibration data set with 8 fresh (15–168 μS/cm) lakes in Cameroon, West Africa, and one hypersaline desert lake in Chad. This experiment yielded poorer error statistics, primarily because the need to amalgamate East and West African sister taxa reduced overall taxonomic resolution and increased the mean tolerance range of retained taxa. However, the merged data set constrained better the salinity optimum of several freshwater taxa, and further increased the probability of finding good modern analogues. We then used chironomid stratigraphic data and independent proxy reconstructions from two fluctuating lakes in Kenya to compare the performance of new and previous African salinity-inference models. This analysis revealed significant differences between the various numerical techniques in reconstructed salinity trends through time, due to their different sensitivity to the presence or relative abundance of certain key taxa, combined with the above-mentioned threshold faunal response to salinity change. Simple WA and WMAT produced ecologically sensible reconstructions because their step-like change in inferred conductivity near 3000 μS/cm mirrors the relatively rapid transitions between fresh and saline lake phases associated with climate-driven lake-level change in shallow tropical closed-basin lakes. Statistical camouflaging of this threshold faunal response in WA-PLS and ML models resulted in less trustworthy reconstructions of past salinity in lakes crossing the freshwater-saline boundary. We conclude that selection of a particular inference model should not only be based on statistical performance measures, but consider chironomid community ecology in the study region, and the amplitude of reconstructed environmental change relative to the modern environmental gradient represented in the calibration data set.

Sub-fossil Chironomidae from East Africa. 2. Chironominae (Chironomini and Tanytarsini)

This paper and a companion article present illustrated guides to the identification of sub-fossil chironomid larvae (Insecta: Diptera: Chironomidae) preserved in the sediments of low- and mid-elevation lakes in East Africa. They are based on analysis of surface-sediment death assemblages from 61 lakes located in the humid to semi-arid environments in equatorial East Africa (Uganda, Kenya, Tanzania), supplemented with similar surface-sediment samples from 12 lakes in the Horn of Africa (Ethiopia), and sub-recent core samples from six lakes in Kenya and two in Uganda. We analyzed about 11,000 specimens and identified 98.4% of these to species, species group, genus, or tribe level, depending on current α-taxonomic knowledge of the various considered genera and the taxonomic resolution of preserved diagnostic features. We distinguished 90 different sub-fossil morphotypes, of which 16 are Tanypodinae, 19 are Orthocladiinae, and 55 are Chironominae. In this paper we focus on the subfamily Chironominae (tribes Chironomini and Tanytarsini). The diagnostic characters distinguishing these morphotypes from each other resemble differences at the species level in the better-known Holarctic fauna, hence we consider most of our morphotypes equivalent to morphological species or groups of closely related species. Given that core samples yielded only seven morphotypes not also found in the surface-sediment samples, the current inventory of 90 taxa likely represents the large majority of distinct sub-fossil chironomid larval types to be found in East African lakes, excluding the few very large Rift lakes, cold-water lakes above treeline, and special standing-water environments such as fens and bogs. Consistent use of a single set of morphological characters to identify both fossil and living chironomid larvae would ensure exchangeability of information between modem and paleoenvironmental studies on aquatic invertebrate communities in African lakes, and increase the relevance of paleoenvironmental reconstructions to water-quality evaluations aimed at sustainable management of scarce, fluctuating surface-water resources in tropical East Africa.

Sub-fossil Chironomidae from East Africa. 1. Tanypodinae and Orthocladiinae

This paper and a companion article present illustrated guides to the identification of sub-fossil chironomid larvae (Insecta: Diptera: Chironomidae) preserved in the sediments of low- and mid-elevation lakes in East Africa. They are based on analysis of surface-sediment death assemblages from 61 lakes located in the humid to semi-arid environments of equatorial East Africa (Uganda, Kenya, Tanzania), supplemented with similar surface-sediment samples from 12 lakes in the Horn of Africa (Ethiopia), and sub-recent core samples from six lakes in Kenya and two in Uganda. We analyzed about 11,000 specimens and identified 98.4% of these to species, species group, genus, or tribe level depending on current α -taxonomic knowledge of the various genera considered and the taxonomic resolution of preserved diagnostic features. We distinguished 90 different sub-fossil morphotypes, of which 16 are Tanypodinae, 19 are Orthocladiinae, and 55 are Chironominae. Diagnostic characters distinguishing these morphotypes from each other resemble differences at the species level in the better-known Holarctic fauna, hence we consider most of our morphotypes equivalent to morphological species or groups of closely related species. In this paper we focus on the Tanypodinae and Orthocladiinae, with special attention to the high taxon richness among the Pentaneurini. Patterns of cephalic setation were found to facilitate identification of Tanypodinae both at the genus and species level, and contributed to improved taxonomic resolution in sub-fossil East African material. High taxon richness and numerical abundance of the Orthocladiinae in our study lakes indicates that a considerable number of African Orthocladiinae is adapted to warm standing-water environments.

Satellite tracking Lesser Flamingo movements in the Rift Valley, East Africa: pilot study report

The Lesser Flamingo (Phoeniconaias minor) is thought to be highly nomadic. In East Africa, the number of individuals on a given lake has been shown to double or halve in a period of just two weeks. In general, interlake movements are believed to take place mostly at night. However, movement timing and patterns for individual birds are unknown. Between 12 and 23 October 2002, we affixed two solar-powered and two battery-powered satellite transmitters (PTTs) to four large (>2kg) adult male Lesser Flamingos at Lake Bogoria, Kenya. During the first three months, the four birds exhibited markedly different movement patterns. One moved 687km, making seven visits to four different lakes (mean stay: 11.4d). Another made five visits to only three different lakes (mean stay: 18.5 days), travelling only 263km. On two occasions, it remained on one lake for long periods (34 days and 70 days). A third moved among lakes in Kenya and Tanzania 44 times, visiting nine different lakes, spending an average of only 2.3 days at each and travelling a total of 4 792km in the process. The fourth is believed to have been predated on Lake Bogoria at the end of the first month. During the last six months of the study, the most active bird settled down and the behaviour of the three remaining birds was much more similar. They each spent long periods of time (e.g. 45-137d) at just one or two sites. During the study period, one bird made several short (21-81km) interlake flights during daylight hours. Flight speed was estimated to be approximately 68km h-1 during the only flight when speed could be calculated. Both solar-powered PTTs functioned well; light reaching the solar panels was not impaired by feathers or dried mineral crystals, both initial concerns. The solar-powered PTT with a pre-set 'on/off' duty cycle performed much better than the other with no pre-set duty cycle, indicating that small solar-powered units need substantial 'off' time to recharge their batteries, even in areas with 12h of sunlight daily. The key site network for Lesser Flamingos in East Africa consists of seven alkaline lakes in Kenya and Tanzania (Logipi, Bogoria, Nakuru, Elmenteita, Natron, Manyara and Eyasi) and an ephemeral fresh water wetland in central Tanzania (Bahi Swamp). The conservation status of these eight sites varies from well-protected (lakes Bogoria, Nakuru and Manyara) to completely unprotected (Logipi, Natron, Eyasi and Bahi Swamp), with Elmenteita being partially protected.

Staurophora Caljonii Spec. Nov. (Bacillariophyceae, Anomoeoneidaceae), a New Halophilic Diatom Species from Sub-Recent Lake Deposits in Kenya

Fossil diatom analyses of lake-sediment cores representing the last ∼250 years of Lakes Oloidien and Sonachi in the Eastern (Gregory) Rift Valley of central Kenya yielded a new diatom species, described here as Staurophora caljonii spec. nov. (Bacillariophyceae, Anomoeoneidaceae) on the basis of light and electron microscopic investigations of its frustule morphology. This presumably benthic halophilic species is known only from saline phases in the recent history of two sodium-bicarbonate (soda) lakes, when diatom-inferred conductivity was around 10 000 μS cm−1. It has not been found in the modern diatom flora from saline Rift Valley lakes in Kenya (Sonachi, Nakuru, Elementeita) or Ethiopia (Abiyata, Langano), nor in Lake Oloidien, which is a freshwater lake nowadays. Its fossil distribution suggests that semi-permanent saline wetlands are its natural habitat. The closest modern relative of Staurophora caljonii appears to be Stauroneis legleri Hustedt, a taxon known only from a salt lake in Austria. Additional, a light microscopic description of the frustule of S. legleri is given as well as some scanning electron microscopic characteristics.

Aquatic biodiversity and saline lakes: Lake Bogoria National Reserve, Kenya

Lake Bogoria, in the Rift Valley of Kenya is an extreme saline lake (conductivity 40–80 mS cm-1, alkalinity 1500 m equ 1-1). It is hydrologically more stable than the other, endorheic lakes in Kenya, because it is deep — maximum depth at present just over 10 m in an area of 3000 ha — and so does not have periods when it is dry. It is ecologically simple, with only one species dominating the phytoplankton — the cyanobacterium ‘spirulina’, Arthrospira fusiformis. Its biomass and productivity were very high — biomass between 38 and 365 μg 1-1 chlorophyll ‘a’ and 3.4–21 x 103 coils ml-1 and net production between 0.24 and 1 gm C m3 h, the latter in a narrow zone of less than a metre. There were no macro-zooplankton in the plankton and the only grazer of A. fusiformis was the lesser flamingo, Phoeniconaias minor, which occurred irregularly in very high concentrations (in excess of 1 x 106). Detritivory in the benthos was effected by a single chironomid species, Paratendipes sp., at a maximum density of 4 x 104 m-2. The mean daily emergence of adult chironomids was estimated to be 1 x 103 m-2, the maximum 3. There was no littoral plant community within the lake but 44 dicotyledonous and 31 monocotyledonous plant species in the drawn-down zone and adjacent to it. A diverse draw-down terrestrial invertebrate fauna, only superficially described here, processed the flamingo feathers and carcasses, with other detritus such as chironomid pupal exuviae and decaying A. fusiformis scum. About 50 bird species depended upon the chironomids, either as they emerged through the water column as flying adults or later on the shoreline as floating pupal exuvia and dead adults. The lake has high conservation value because of three bird species in particular — lesser flamingo, Cape teal and black-necked grebe. The former provides real economic value in a region otherwise impoverished, because of the spectacle of tens of thousands of flamingos set against the landscape of hot springs and fumaroles at the lake edge, which draws 15 000 visitors per annum. P. minor has experienced three periods during the past ten years when major mortalities have occurred, the last of which killed 700 birds day-1. This could have involved as many as 200 000 birds (about 1/5th of the maximum population at this lake) if mortality was at a constant rate for the nine months it was observed. Causes of mortality have been suggested as avian tuberculosis, poisoning from cyanobacterial toxins or from heavy metal contamination at Lake Nakuru, but it is still not yet clear what contribution each makes to the problem.

Patterns of variation in waterbird numbers on four Rift Valley lakes in Kenya, 1991–1999

Waterbird populations were censused each January from 1991 to 1999 at Lakes Naivasha, Elmenteita and Nakuru and from 1992 at Lake Bogoria. These shallow lakes in the Kenyan Rift Valley fluctuate greatly in water level and alkalinity. All but Naivasha are usually saline; Nakuru and Elmenteita at times support fish, while Bogoria is fishless. A standardized logarithmic index of relative abundance (value 1.0 for the mean) was calculated for each major waterbird group at each lake, and for Naivasha, Elmenteita and Nakuru combined (‘combined lakes’). Its variance was used to compare levels of variation within and across lakes. For the combined lakes, there was high variance in large piscivores (whether combined or separated into groups), grebes, rallids and flamingos. There was low variance in Palaearctic waders (combined or separated into groups), ibises and spoonbills and birds of prey. However, the lakes generally showed idiosyncratic patterns of variation across the different groups. Variance in the indices for birds of prey and kingfishers were consistently low (max. 0.036 and 0.042, respectively), but no group had consistently high variance across all sites. The variance for all birds (other than flamingos) combined was low (0.018 – 0.085) and similar across all lakes and for combined lakes (0.018). For the combined lakes, the variance for flamingos was five times higher than for all other birds (p<0.05), though the two variances were almost equal for Bogoria. Flamingos were the most variable at Naivasha (variance 0.281) followed by Elmenteita (0.177), Nakuru (0.101) and Bogoria (0.024, and significantly lower than all the rest, p<0.05). This was opposite in order to the mean numbers of flamingos recorded at each site. Large piscivores were relatively stable at Naivasha (variance 0.005) but much more variable at Elmenteita (0.199) and Nakuru (0.269). Patterns of variation within lakes were correlated for some groups, such as waders at Naivasha and large piscivores at Nakuru. These correlations could be related to local ecological conditions. However, there were few large correlations across sites, and these were mainly direct. There was, therefore, no evidence that a fixed population of waterbirds was distributing itself across sites according to conditions. Each lake thus seems to represent and independent entity, while the waterbirds they host evidently move much more widely afield than this portion of the Rift Valley.

Inter-lake movements of the Lesser Flamingo Phoeniconaias minor and their conservation in the saline lakes of Kenya

Maina, J.G. 2000. Inter-lake movements of the Lesser Flamingo Phoeniconaias minor and their conservation in the saline lakes of Kenya. Ostrich 71 (1 & 2): 126. The Lesser Flamingo Phoeniconaias minor is the only algivore in the saline lakes of Kenya occurring in spectacular assemblages that form the tourism base. The flamingos show unpredictable, spontaneous, “nomadic” movements between the saline lakes whose precipitating ecological factors were not well established. Food, conductivity, breeding, predation and fresh water availability were regarded as the primary factors in spite of their global coverage in explaining animal movements. Evidence is emerging that food, especially algal species composition, density, and lake levels are the primary driving factors for these inter-lake movements, with other factors being consequences of these. Algal species composition and lake levels are subject to limnological processes in the lakes, climatic conditions and human activities in the catchment of the saline lakes. Environmental degradation is now a critical factor influencing the limnology of these fragile ecosystems with far ranging consequences on lake levels, algal species composition and succession. These changes determine flamingo utilization patterns within and between the lakes. This calls for a review of the conservation status and management of the saline lakes, home to a few but highly specialised species.

Comparative limnology, species diversity and biomass relationship of zooplankton and phytoplankton in five freshwater lakes in Kenya

Comparative studies on the limnology, species diversity and standing stock biomass of phytoplankton and zooplankton in five freshwater lakes, Naivasha and Oloidien, Ruiru, Masinga and Nairobi reservoirs, were undertaken. Phytoplankton chlorophyll a, dissolved oxygen and temperature were also measured. Thermocyclops oblongatus (Copepoda) was dominant in all the lakes. Ceriodaphnia cornuta and Diaphanosoma excisum (Cladocera) dominated in lakes Naivasha and Oloiden, whereas in Ruiru, Masinga and Nairobi reservoirs, Brachionus angularis and Hexarthra mira (Rotifera) were the dominant zooplankters. Phytoplankton biomass as chlorophyll a was lowest in Ruiru dam 5.64 ± 4.0 µg l-1 and highest in the eutrophic Nairobi dam 71.5 ± 12.02 µg l-1. The endorheic lakes Naivasha and Oloidien showed medium values of 24.5 ± 4.0 µg l-1.

Irrigation activities and institutions in Kenya's Lake Victoria Basin

Irrigation activities in Kenya range from large‐scale government‐owned schemes involving thousands of acres on which farmers work for wages to small individually owned and irrigated plots of three or four acres. This paper examines the institutions and operational workings of the government schemes as well as the privately owned plots. In general the most successful irrigation schemes are those which are organized and run by individuals or by private groups with government agencies and NGOs providing technical support.

Photoactive retinal pigments in haloalkaliphilic bacteria.

Light-induced fast transient absorbance changes were detected by time-resolved spectroscopy in 38 of 51 haloalkaliphilic isolates from alkaline salt lakes in Kenya and the Wadi Natrun in Egypt. They indicate the presence of two retinal pigments, Pf and Ps, which undergo cyclic photoreactions with half-times of 2 ms and 500 ms respectively. Pf absorbs maximally near 580 nm and Ps near 500 nm. The pigments differ in their sensitivity to hydroxylamine and detergent bleaching and the photoreactions of Pf are strongly dependent on chloride concentration. Of the 38 pigment-containing strains, 29 possess both Pf and Ps, 9 possess only Ps. Inhibition of retinal synthesis with nicotine blocks pigment formation and addition of retinal restores it. Hydroxylamine-bleached pigments can be reconstituted with retinal or retinal analogues. Their similarity to the retinal pigments of Halobacterium halobium strongly suggests that they are also rhodopsin-like retinyledene proteins. Pf in all properties tested is almost identical to halorhodopsin, the light-driven chloride pump of H. halobium, and may serve the same function in the haloalkaliphiles. Ps has photocycle kinetics similar to sensory rhodopsin and a far-blue-shifted long-lived photocycle intermediate, but its ground state absorption maximum is near 500 nm instead of 587 nm. We have not found a bacteriorhodopsin-like pigment in the haloalkaliphiles.

Responses of phytoplankton to experimental fertilization with ammonium and phosphate in an African soda lake.

Phytoplankton abundance in tropical lakes is more often judged to be limited by nitrogen than phosphorus, but seldom does the evidence include controlled enrichments of natural populations. In January 1980 we performed the first experimental fertilization in an equatorial African soda lake, Lake Sonachi, a small, meromictic volcanic crater lake in Kenya. During our study the natural phytoplankton abundance was ca. 80 μg chl a/l, and the euphotic zone PO4 and NH4 concentrations were less than 0.5 μM. In the monimolimnion PO4 reached 180 μM and NH4 reached 4,600 μM. Replicate polyethylene cylinders (5 m long, 1.2 m3) were enriched to attain 10 μM PO4 and 100 μM NH4. Phytoplankton responses were measured as chlorophyll, cell counts and particulate N, P and C. After two days, the chlorophyll increase in the P treatment was significantly higher than the control (P<0.01) while the N treatment was not. After five days the molar N/P ratio of seston was the same in the N treatment and control (23) but only 6 in the P treatment. The molar N/P ratio of seston in an unenriched Lake Sonachi sample was 21 and in samples from Lakes Bogoria and Elmenteita, two shallow soda lakes in Kenya, the ratios were 12 and 70 respectively. We conclude that limitation of phytoplankton abundance by phosphorus can occur even in some tropical African soda lakes.

Photosynthetic rates of phytoplankton in East African alkaline, saline lakes1

Photosynthetic rates were calculated in six myxophycean‐dominated alkaline, saline lakes in Kenya and Tanzania from changes in dissolved O2 in light and dark bottles and from diurnal variations in dissolved O2. Rates of gross photosynthesis are exceptionally high for Lake Nakuru, Kenya, by the diurnal free‐water technique (e.g. 36 g O2 m−2 day−1). Gross photosynthesis in Lake Nakuru was compared for two consecutive days: on the first day pronounced thermal stratification developed and the dissolved O2 reached 340% saturation in the upper half meter; on the second day wind‐driven turbulence circulated the algae to depths often greater than 2 m in water with Secchi disk visibility of only 15 cm.Because of analytical difficulties in measuring dissolved O2 in soda lakes, laboratory experiments were conducted to determine the reliability of the titrimetric (Winkler, Miller), gasometric (Scholander), and polarographic (oxygen probe) methods. The polarographic technique was the most suitable for determinations of dissolved O2 in the field.

The Fluorine Content and Food Value of Kenya Lake Fish

The Fluorine Content and Food Value of Kenya Lake Fish

Changes in Level of Lake Naivasha, Kenya, during Postglacial Times

STRANDLINES high above the present levels of three small lakes in Kenya provide some of the earliest-recognized evidence for past climatic changes in tropical Africa. The terraces above Lakes Nakuru, Naivasha and Elmenteita were studied intensively by Nilsson1,2 more than 30 years ago, and are one of the major bases on which the pluvial theory of Pleistocene climates in Africa was constructed. Despite later disagreements on the number and interpretation of these strandlines, it is still generally accepted that they provide good evidence for at least one pluvial period (the Gamblian) and two lesser post-pluvial wet phases (the Makalian and Nakuran)3,4.